Ceiling fans are conventionally constructed using one of two motor types: type (A) where a central shaft is attached to a stator, where said shaft is stationary while the blades are attached to a rotor which rotates about the periphery of the stator, or; type (B) where the central shaft is attached to the rotor with the blades attached thereto and said shaft rotates with both rotor and shaft surrounded or encompassed by the stator.
Fan motors of the type (A), where the rotor rotates around the periphery of the stator, require the rotor to be held in a fixed longitudinal and lateral position relative to the shaft and the stator. Typically this is achieved by the use of two bearings and two motor housings containing said bearings, these housings being made of resilient material such as sheet metal and of a thickness that yields a small amount of elastic deformation thus allowing them to be pressed around or otherwise attached to the rotor. The rotor is thus prevented from rectilinear motion but is allowed curvilinear motion. ‘Steps’ on the shaft allow correct longitudinal positioning of the bearings. The blades of the ceiling fan may be attached to the rotor by various means. The stationary body of the fan (if any), suspension mechanism, light fittings and trimmings may also be attached to the stationary shaft where it projects from the bearings by various means. Motors of this type are typically split-capacitor induction motors.
Fan motors of the type (B), where the stator is fixed around the periphery of the rotor and the rotor and shaft rotate within the stator, require the rotating shaft to be held in a fixed longitudinal and lateral position relative to the stator and any devices attached to it. Typically two bearings, or one bearing plus a bushing, are pressed into the stator, or housing made of resilient material such as sheet metal and of a thickness that yields a small amount of elastic deformation thus allowing it to be pressed around or otherwise attached to the stator. Steps on the shaft may allow correct longitudinal positioning of the bearings. The rotor and shaft is thus prevented from rectilinear motion but allowed curvilinear motion. The blades of the ceiling fan may be attached to the shaft by various means. The stationary body of the fan (if any), suspension mechanism, light fittings and trimmings may also be attached to the stator by various means. Motors of this type are typically split-capacitor or shaded-pole induction motors or brushless DC motors.
Electric motors of most types in general, when used for this purpose, require the rotor to be stabilised laterally so the electromotive forces generated between stator windings and rotor windings is translated into curvilinear motion and do not result in the rotor being pulled sideways and into contact with the stator. This is usually achieved by the bearings being spaced a suitable distance apart and the material housing the bearings being suitably resilient either by nature of the materials themselves or forces imposed by mechanical design.
For motors of the type (A) or (B), when used with ceiling fans, the bearings or combination of bearings and bushes add considerable height and bulk to the motor assembly, before taking into account the attachment of blades and the stationary body of the fan (if any), suspension mechanism, light fittings and trimmings. The height of the motor assemblies described as types (A) and (B) prevents conventional ceiling fans from adopting slim or thin body profiles.
The attachment mechanism residing between the body of the ceiling fan and the suspension mechanism requires attachment to the stationary shaft (as per type (A)) or to the stator (as per type (B)) and in either case adequate clearance must be provided from rotating parts, which again increases the height required by the body of the fan. This further restricts the minimum profile achievable with motors of these designs.
Accordingly, it is an object of the invention to provide a bearing assembly for a ceiling mounted fan that facilitates a slimmer or flatter design of a fan hub.